Plant community responses to mechanical site preparation in northern interior British Columbia

Abstract

Ten-year response of plant communities to disk trenching, plowing, rotoclearing and windrow burning was studied on two contrasting sites to address concerns that mechanical site preparation reduces structural and species diversity. Cover and height of all species on randomly located subplots within 0.05- to 0.075-ha treatment plots were used to develop indices of volume, structural diversity, and species diversity; to ordinate the plots; and to correlate species diversity with crop-tree performance. At both sites, community response was strongly influenced by the severity of site preparation. On a boreal site dominated by willow (Salix L. spp.), green alder (Alnus crispa (Ait.) Pursh ssp. crispa) and trembling aspen (Populus tremuloides Michx.), site preparation increased structural diversity and had little effect on species diversity. High-severity treatments increased non-native species abundance 10- to 16-fold while only marginally enhancing growth of planted white spruce (Picea glauca (Moench) Voss) over medium-severity treatments. On a nutrient-poor sub-boreal site, species diversity declined with increasing treatment severity and with increasing lodgepole pine (Pinus contorta var. latifolia Engelm.) stem volume. Velvet-leaved blueberry (Vaccinium myrtilloides Michx.) was highly sensitive to mechanical disturbance. Moderate mechanical treatments appear to improve conifer performance while causing little change to plant communities, but high severity treatments can cause substantial change.

Hard pine stem rusts on lodgepole pine at a site-preparation study in sub-boreal British Columbia: effects over 24 years

“…This does not appear to have been an important factor at the Bednesti site, however, because there was no treatment effect on comandra blister rust cumulative infection rate. A related study also reported that the treatments at Bednesti did not stimulate large increases in the herbaceous plant community (Haeussler et al 1999), which indirectly suggests little effect on G. lividum.…”

Yield Implications of Site Preparation Treatments for Lodgepole Pine and White Spruce in Northern British Columbia

“…In boreal forests white spruce establishment is often limited by severe vegetation competition and unfavorable soil conditions, therefore treatments that affect these factors have proven to increase growth and survival of spruce (e.g., [8,26,28,48]). Both mechanical site preparation treatments and the removal of competing vegetation, by applying herbicide or fire, result in a shift in the plant community from tall shrubs (e.g., green alder and willow), as in the untreated, to mainly grasses and forbs [22,28,49]. At the Inga Lake site the treatment effect (e.g., decreased soil density and improved nutrient availability) was still significant 15 years after planting [8], but a later study at age 20 found that early microsite amelioration caused by the establishment treatments was ceasing and was having less impact on spruce growth than the negative response to competing vegetation [28].…”

Managing tree plantations as novel socioecological systems: Australian and North American perspectives

“…These techniques create a heterogeneous microtopography that could provide habitat for vascular understory plant species (Haeussler et al 1999;Ramovs and Roberts 2003), as well as hatching habitat for amphibians (Semlitsch et al 2009). …”